So-called “instant” or “quick” connection couplers are known that comprise a tubular body arranged to receive a pipe end and provided internally with means for retaining said pipe end. These means are generally constituted by a deformable washer whose inside circumference is subdivided into a plurality of teeth or claws which project into the tubular body. When the pipe end is inserted into the tubular body, the pipe end lifts the teeth so that their free ends come to rest against the outside surface of the pipe end. When pressure is raised in the circuit in which the coupler is installed, the pipe end moves back a little prior to the teeth coming to bite into the outside surface of the pipe end and serving to retain it. During insertion of the pipe end, the teeth which rub against the outside surface of the pipe end run the risk of scratching it.
Unfortunately, the coupling is generally sealed by means of an O-ring that fits tightly around the pipe end, such that scratches run the risk of constituting leakage zones or of damaging the sealing ring to such an extent that it can no longer perform its function. It would be possible to increase the flexibility of the washer in order to reduce the force exerted on the outside surface of the pipe end by the teeth. However that would also reduce the strength of retention and would increase the distance through which the pipe end moves backwards when pressure is applied to the circuit. Unfortunately, such backward movement produces a zone in which fluid is retained, which zone must be kept as small as possible, in particular in circuits that convey a liquid that is perishable.
Quick-connection couplers are also known comprising a tubular body having a latch mounted to move thereon radially between a locking position in which the latch possesses a portion projecting into the tubular body, and an unlocking position in which said portion is retracted from the tubular body. The risks of the pipe end being scratched or moving backwards are then small. However, it is necessary to provide a setback either directly in the pipe end or in an endpiece mounted on the pipe end in order to co-operate with the latch of the coupler.